Focused on the non-statlonarity and real-time analysis of signal in flutter test with progression variable speed （FTPVS）, a new method of recursive time-frequency analysis is presented. The time-varying system is tr...Focused on the non-statlonarity and real-time analysis of signal in flutter test with progression variable speed （FTPVS）, a new method of recursive time-frequency analysis is presented. The time-varying system is tracked on-line by building a time-varying parameter model, and then the relevant parameter spectrum can be obtained. The feasibility and advantages of the method are examined by digital simulation. The results of FTPVS at low-speed wind-tunnel promise the engineering application perspective of the method.展开更多
Owing to the advantages of wire-driven parallel manipulator, a new wire-driven parallel suspension system for airplane model in low-speed wind tunnel is constructed, and the methods to measure and calculate the aerody...Owing to the advantages of wire-driven parallel manipulator, a new wire-driven parallel suspension system for airplane model in low-speed wind tunnel is constructed, and the methods to measure and calculate the aerodynamic parameters of the airplane model are studied. In detail, a static model of the wire-driven parallel suspension is analyzed, a mathematical model for describ- ing the aerodynamic loads exerted on the scale model is constructed and a calculation method for obtaining the aerodynamic parameters of the model by measuring the tension of wires is presented. Moreover, the measurement system for wire tension and its corresponding data acquisition system are designed and built. Thereafter, the wire-driven parallel suspension system is placed in an open return circuit low-speed wind tunnel for wind tunnel tests to acquire data of each wire tension when the airplane model is at different attitudes and different wind speeds. A group of curves about the parameters for aerodynamic load exerted on the airplane model are obtained at different wind speeds after the acquired data are analyzed. The research results validate the feasibility of using a wire-driven parallel manipulator as the suspension system for low-speed wind ttmnel tests.展开更多
Piled embankments,which offer many advantages,are increasingly popular in construction of high-speed railways in China.Although the performance of piled embankment under static loading is well-known,the behavior under...Piled embankments,which offer many advantages,are increasingly popular in construction of high-speed railways in China.Although the performance of piled embankment under static loading is well-known,the behavior under the dynamic train load of a high-speed railway is not yet understood.In light of this,a heavily instrumented piled embankment model was set up,and a model test was carried out,in which a servo-hydraulic actuator outputting M-shaped waves was adopted to simulate the process of a running train.Earth pressure,settlement,strain in the geogrid and pile and excess pore water pressure were measured.The results show that the soil arching height under the dynamic train load of a high-speed railway is shorter than under static loading.The growth trend for accumulated settlement slowed down after long-term vibration although there was still a tendency for it to increase.Accumulated geogrid strain has an increasing tendency after long-term vibration.The closer the embankment edge,the greater the geogrid strain over the subsoil.Strains in the pile were smaller under dynamic train loads,and their distribution was different from that under static loading.At the same elevation,excess pore water pressure under the track slab was greater than that under the embankment shoulder.展开更多
The current method of estimating the fatigue life of railway structures is to calculating the equivalent stress amplitude based on the measured stress data. However, the random of the measured data is not considered. ...The current method of estimating the fatigue life of railway structures is to calculating the equivalent stress amplitude based on the measured stress data. However, the random of the measured data is not considered. In this paper, a new method was established to compute the equivalent stress amplitude to evaluate the fatigue damage based on the measurable randomness, since the equivalent stress is the key parameter for assessment of structure fatigue life and load derivation. The equivalent stress amplitude of a high-speed train welded bogie frame was found to obey normal distribution under uniform operation route that verified by on-track dynamic stress data, and the proposed model is, in effect, an improved version of the mathematical model used to calculate the equivalent stress amplitude. The data of a long-term, on-track dynamic stress test program was analyzed to find that the normal distribution parameters of equivalent stress amplitude values differ across different operation route. Thus, the fatigue damage of the high-speed train welded bogie frame can be evaluated by the proposed method if the running schedule of the train is known a priori. The results also showed that the equivalent stress amplitude of the region connected to the power system is more random than in other regions of the bogie frame.展开更多
Based on three kinds of dynamic test of MEMS, a dynamic system for the vibration test of micro machined gyroscope based on high speed photography is introduced. Firstly, the architecture of the system hardware is intr...Based on three kinds of dynamic test of MEMS, a dynamic system for the vibration test of micro machined gyroscope based on high speed photography is introduced. Firstly, the architecture of the system hardware is introduced. Secondly, the image tracking performance is compared by the test using the template matching algorithm, the mean shift algorithm and the SURF algorithm. The vibration curve shows that high speed photograph combined with SURF algorithm is faster, more ac- curate, and more suitable for the vibration test of micro machined gyroscope. After the frequency a- nalysis and related interpolation, more characteristics of micro gyroscope can be obtained.展开更多
针对内埋舱武器性能鉴定试飞中机弹分离相对位姿测量需求,提出了一种基于高速影像的内埋舱武器分离位姿测量方法。通过加装带有弯管镜头的高速摄像机阵列,实现内埋弹舱狭小空间内弹体分离全过程高速影像数据的分段获取;采用结合机载空...针对内埋舱武器性能鉴定试飞中机弹分离相对位姿测量需求,提出了一种基于高速影像的内埋舱武器分离位姿测量方法。通过加装带有弯管镜头的高速摄像机阵列,实现内埋弹舱狭小空间内弹体分离全过程高速影像数据的分段获取;采用结合机载空间参考点不确定性的相机外参解算、基于You Only Look Once version 8(YOLOv8)的标志点智能检测、基于边缘灰度梯度正交迭代的十字标中心坐标自动提取、直线约束下的多视角非交叠影像测量等方法,实现机载高速摄像机分布快速标定、小视场成像条件下弹体表面标志点亚像素坐标自动提取、机载高速摄像机抖动下的外参动态修正以及武器分离相对位姿分段测量等功能。经地面试验验证,该方法位置解算均方根误差不大于2 mm,满足飞行试验测试精度要求。展开更多
文摘Focused on the non-statlonarity and real-time analysis of signal in flutter test with progression variable speed （FTPVS）, a new method of recursive time-frequency analysis is presented. The time-varying system is tracked on-line by building a time-varying parameter model, and then the relevant parameter spectrum can be obtained. The feasibility and advantages of the method are examined by digital simulation. The results of FTPVS at low-speed wind-tunnel promise the engineering application perspective of the method.
基金National Natural Science Foundation of China (50475099)
文摘Owing to the advantages of wire-driven parallel manipulator, a new wire-driven parallel suspension system for airplane model in low-speed wind tunnel is constructed, and the methods to measure and calculate the aerodynamic parameters of the airplane model are studied. In detail, a static model of the wire-driven parallel suspension is analyzed, a mathematical model for describ- ing the aerodynamic loads exerted on the scale model is constructed and a calculation method for obtaining the aerodynamic parameters of the model by measuring the tension of wires is presented. Moreover, the measurement system for wire tension and its corresponding data acquisition system are designed and built. Thereafter, the wire-driven parallel suspension system is placed in an open return circuit low-speed wind tunnel for wind tunnel tests to acquire data of each wire tension when the airplane model is at different attitudes and different wind speeds. A group of curves about the parameters for aerodynamic load exerted on the airplane model are obtained at different wind speeds after the acquired data are analyzed. The research results validate the feasibility of using a wire-driven parallel manipulator as the suspension system for low-speed wind ttmnel tests.
基金National Natural Science Foundation of China under Grant Nos.51622803,51378177 and 51420105013the 111 Project under Grant No.B13024
文摘Piled embankments,which offer many advantages,are increasingly popular in construction of high-speed railways in China.Although the performance of piled embankment under static loading is well-known,the behavior under the dynamic train load of a high-speed railway is not yet understood.In light of this,a heavily instrumented piled embankment model was set up,and a model test was carried out,in which a servo-hydraulic actuator outputting M-shaped waves was adopted to simulate the process of a running train.Earth pressure,settlement,strain in the geogrid and pile and excess pore water pressure were measured.The results show that the soil arching height under the dynamic train load of a high-speed railway is shorter than under static loading.The growth trend for accumulated settlement slowed down after long-term vibration although there was still a tendency for it to increase.Accumulated geogrid strain has an increasing tendency after long-term vibration.The closer the embankment edge,the greater the geogrid strain over the subsoil.Strains in the pile were smaller under dynamic train loads,and their distribution was different from that under static loading.At the same elevation,excess pore water pressure under the track slab was greater than that under the embankment shoulder.
基金Supported by National Key Research and Development Program of China(Grant No.2018YFB1201704)National Natural Science Foundation of China(Major Program,Grant No.11790281)
文摘The current method of estimating the fatigue life of railway structures is to calculating the equivalent stress amplitude based on the measured stress data. However, the random of the measured data is not considered. In this paper, a new method was established to compute the equivalent stress amplitude to evaluate the fatigue damage based on the measurable randomness, since the equivalent stress is the key parameter for assessment of structure fatigue life and load derivation. The equivalent stress amplitude of a high-speed train welded bogie frame was found to obey normal distribution under uniform operation route that verified by on-track dynamic stress data, and the proposed model is, in effect, an improved version of the mathematical model used to calculate the equivalent stress amplitude. The data of a long-term, on-track dynamic stress test program was analyzed to find that the normal distribution parameters of equivalent stress amplitude values differ across different operation route. Thus, the fatigue damage of the high-speed train welded bogie frame can be evaluated by the proposed method if the running schedule of the train is known a priori. The results also showed that the equivalent stress amplitude of the region connected to the power system is more random than in other regions of the bogie frame.
文摘Based on three kinds of dynamic test of MEMS, a dynamic system for the vibration test of micro machined gyroscope based on high speed photography is introduced. Firstly, the architecture of the system hardware is introduced. Secondly, the image tracking performance is compared by the test using the template matching algorithm, the mean shift algorithm and the SURF algorithm. The vibration curve shows that high speed photograph combined with SURF algorithm is faster, more ac- curate, and more suitable for the vibration test of micro machined gyroscope. After the frequency a- nalysis and related interpolation, more characteristics of micro gyroscope can be obtained.
文摘针对内埋舱武器性能鉴定试飞中机弹分离相对位姿测量需求,提出了一种基于高速影像的内埋舱武器分离位姿测量方法。通过加装带有弯管镜头的高速摄像机阵列,实现内埋弹舱狭小空间内弹体分离全过程高速影像数据的分段获取;采用结合机载空间参考点不确定性的相机外参解算、基于You Only Look Once version 8(YOLOv8)的标志点智能检测、基于边缘灰度梯度正交迭代的十字标中心坐标自动提取、直线约束下的多视角非交叠影像测量等方法,实现机载高速摄像机分布快速标定、小视场成像条件下弹体表面标志点亚像素坐标自动提取、机载高速摄像机抖动下的外参动态修正以及武器分离相对位姿分段测量等功能。经地面试验验证,该方法位置解算均方根误差不大于2 mm,满足飞行试验测试精度要求。
